One of the primary methods presently known for generating programs for multi-axis machining systems is to "teach" the machine the program by moving a machining head such as a laser beam cutting nozzle around the desired path (usually a line scribed on a master part, referred to as a scribe line). Points or positions along the scribe line are entered or "taught" by entering their coordinates into the controller and are then stored. These points form the basis for the part machining program that commands the machine to move around the workpiece and perform machining operations at locations along the taught path. After the coordinates of interest are taught to the program, the program is then edited to enter additional information such as feed rates and laser parameters to complete the workpiece program.
Such a method of generating a program for machining a workpiece (generally referred to as "teaching") requires that the machine be positioned very accurately over the scribe line as each point is entered. There are a number of methods used to achieve this accurate positioning. Currently, three methods are primarily used: (1) use of the laser beam at low power, (2) use of a collinear HeNe laser, or (3) use of a probe tip.
Each of these three current methods has shortcomings. Using the laser beam at low power exposes the operator to potentially hazardous laser radiation. The HeNe laser focusses at a different spot than the CO.sub.2 laser beam used for machining and is difficult to align. Probe tips are inaccurate and are prone to damage.